The invention relates to an apparatus for treating containers and in particular to a blowing apparatus for expanding containers. In addition, the invention also relates to a method for expanding containers.
From the prior art, it is known in the context of producing various vessels to expand the latter using a blowing nozzle. To this end, suitable blanks are heated and then are acted upon by compressed air at a pressure in the region of approximately 40 bar through a blowing nozzle. By virtue of this pressure, the container is expanded. It is known from the prior art that a sealing between the blowing apparatus and the container takes place during the actual expansion process, i.e. the process during which the container is expanded with the compressed air, so that the container can be properly expanded. It is known to perform such sealing for example at the upper rim of the mouth of the container or also below the mouth rim.
A mouth will hereinafter be understood to mean a region of the preform which has a collar and a region extending beyond this collar in the direction of the pouring opening. According to one preferred further development, the mouth has a thread. A collar is understood to mean a radially protruding, at least partially circumferential accumulation of material which is preferably configured as a ring. In this case, the collar may be configured as a carrying ring, but also as a securing ring. However, the invention is not limited to the use of the above mouths.
In order to achieve this sealing, in the prior art the blowing piston is lowered onto the vessel and is usually pressed against the latter. In doing so, the contact pressure can be controlled only with relative difficulty. An excessively high pressure on the mouth of the preform may lead to deformations, and an excessively low pressure may result in insufficient sealing between the blowing apparatus and the container.